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Origin of sawtooth domain walls in ferroelectrics

Physical Review B 2020年第6期101卷 060103(R)-060103(R)页

作者： J. Zhang Y.-J. Wang J. Liu J. Xu D. Wang L. Wang X.-L. Ma C.-L. Jia L. Bellaiche School of Microelectronics and State Key Laboratory for Mechanical Behavior of Materials Xi'an Jiaotong University Xi'an 710049 China Shenyang National Laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Wenhua Road 72 110016 Shenyang China State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and Engineering Xi'an Jiaotong University Xi'an 710049 China Electronic Materials Research Laboratory School of Electronic Science and Engineering Xi'an Jiaotong University Xi'an 710049 China Ernst Ruska-Center for Microscopy and Spectroscopy with Electrons Forschungszentrum Jülich GmbH 52425 Jülich Germany Department of Physics and Institute for Nanoscience and Engineering University of Arkansas Fayetteville Arkansas 72701 USA

Domains and domain walls are among the key factors that determine the performance of ferroelectric materials. In recent years, a unique type of domain walls, i.e., the sawtooth-shaped domain walls, has been observed in BiFeO3 and PbTiO3. Here, we build a minimal model to reveal the origin of these sawtooth-shaped domain walls. Incorporating this model into Monte Carlo simulations shows that (i) the competition between the long-range Coulomb interaction (due to bound charges) and short-range interaction (due to opposite dipoles) is responsible for the formation of these peculiar domain walls and (ii) their relative strength is critical in determining the periodicity of these sawtooth-shaped domain walls. Necessary conditions to form such domain walls are also discussed.

关键词： Domain walls Ferroelectric domains Lattice models in condensed matter metropolis algorithm

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Computation of the solid-liquid interfacial free energy in hard spheres by means of thermodynamic integration

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Physical Review E 2020年第4期102卷 042123-042123页

作者： M. Bültmann T. Schilling Physikalisches Institut Albert-Ludwigs-Universitt 79104 Freiburg Germany

We used a thermodynamic integration scheme, which is specifically designed for disordered systems, to compute the interfacial free energy of the solid-liquid interface in the hard-sphere model. We separated the bulk contribution to the total free energy from the interface contribution, performed a finite-size scaling analysis, and obtained for the (100)-interface γ=0.591(11)kBTσ−2.

关键词： Interface & surface thermodynamics Thermal properties Liquid-solid interfaces Finite-size scaling metropolis algorithm

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Quantum many-body scars with chiral topological order in two dimensions and critical properties in one dimension

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Physical Review B 2020年第23期102卷 235106-235106页

作者： N. S. Srivatsa Julia Wildeboer Alexander Seidel Anne E. B. Nielsen Max-Planck-Institut für Physik komplexer Systeme D-01187 Dresden Germany Department of Physics Arizona State University Tempe Arizona 85287 USA Department of Physics Washington University in St. Louis St. Louis Missouri 63130 USA

We construct few-body, interacting, nonlocal Hamiltonians with a quantum scar state in an otherwise thermalizing many-body spectrum. In one dimension, the embedded state is a critical state, and in two dimensions, the embedded state is a chiral topologically ordered state. The models are defined on slightly disordered lattices, and the scar state appears to be independent of the precise realization of the disorder. A parameter allows the scar state to be placed at any position in the spectrum. We show that the level spacing distributions are Wigner-Dyson and that the entanglement entropies of the states in the middle of the spectrum are close to the Page value. Finally, we confirm the topological order in the scar state by showing that one can insert anyons into the state.

关键词： Anyons Quantum scars Topological phases of matter Strongly correlated systems Conformal field theory Exact diagonalization metropolis algorithm

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Field-induced freezing in the unfrustrated Ising antiferromagnet

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Physical Review E 2020年第3期102卷 032112-032112页

作者： Adam Iaizzi Department of Physics National Taiwan University No. 1 Section 4 Roosevelt Road Taipei 10607 Taiwan

We study instantaneous quenches from infinite temperature to well below Tc in the two-dimensional square lattice Ising antiferromagnet in the presence of a longitudinal external magnetic field. Under single-spin-flip metropolis algorithm Monte Carlo dynamics, this protocol produces a pair of magnetization plateaus that prevent the system from reaching the equilibrium ground state except for some special values of the field. We explain the plateaus in terms of local spin configurations that are stable under the dynamics.

关键词： Nonequilibrium statistical mechanics Percolation Spin dynamics Ising model metropolis algorithm

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Emergence of an Ising critical regime in the clustering of one-dimensional soft matter revealed through string variables

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Physical Review E 2020年第4期102卷 042134-042134页

作者： F. Mambretti S. Molinelli D. Pini G. Bertaina D. E. Galli Università degli Studi di Milano Dipartimento di Fisica via Celoria 16 I-20133 Milano Italy Istituto Nazionale di Ricerca Metrologica Strada delle Cacce 91 I-10135 Torino Italy

Soft matter systems are renowned for being able to display complex emerging phenomena such as clustering phases. Recently, a surprising quantum phase transition has been revealed in a one-dimensional (1D) system composed of bosons interacting via a pairwise soft potential in the continuum. It was shown that the spatial coordinates undergoing two-particle clustering could be mapped into quantum spin variables of a 1D transverse Ising model. In this work we investigate the manifestation of an analogous critical phenomenon in 1D classical fluids of soft particles in the continuum. In particular, we study the low-temperature behavior of three different classical models of 1D soft matter, whose interparticle interactions allow for clustering. The same string variables highlight that, at the commensurate density for the two-particle cluster phase, the peculiar pairing of neighboring soft particles can be nontrivially mapped onto a 1D discrete classical Ising model. We also observe a related phenomenon, namely the presence of an anomalous peak in the low-temperature specific heat, thus indicating the emergence of Schottky phenomenology in a nonmagnetic fluid.

关键词： Classical statistical mechanics Nucleation Classical spin chains Ising model metropolis algorithm Monte Carlo methods

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Uniform electron gas at finite temperature by fermionic-path-integral Monte Carlo simulations

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Physical Review E 2020年第3期102卷 033203-033203页

作者： V. S. Filinov A. S. Larkin P. R. Levashov Joint Institute for High Temperatures Russian Academy of Sciences Izhorskaya 13 Bldg 2 Moscow 125412 Russia Moscow Institute of Physics and Technology 9 Institutskiy per. Dolgoprudny Moscow Region 141700 Russia

In this paper we study thermodynamic properties of uniform electron gas (UEG) over wide density and temperature range, using the improved fermionic-path-integral Monte Carlo (FPIMC) method. This method demonstrates a significant reduction of the “fermionic sign problem,” which takes place in standard path-integral Monte Carlo simulations of degenerate fermionic systems. We introduce three basic improvements. The first one is the improved treatment of exchange interaction, achieved by the proper change of variables in the path-integral measure. The second improvement is the inclusion of long-range Coulomb effects into an angle-averaged effective potential, as proposed by Yakub and Ronchi [J. Chem. Phys. 119, 11556 (2003)]. The third improvement is the angle-averaging of an exchange determinant, describing the fermionic exchange interaction not only between particles in the main Monte Carlo cell, but also with electrons in the nearest periodic images. The FPIMC shows very good agreement with analytical data for ideal Fermi gas. For strongly coupled UEG under warm dense matter conditions we compare our total and exchange-correlation energy results with other Monte Carlo approaches.

关键词： High-energy-density plasmas First-principles calculations in plasma physics metropolis algorithm Path-integral Monte Carlo Path-integral methods

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Posterior and predictive inferences for Marshall Olkin bivariate Weibull distribution via Markov chain Monte Carlo methods

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INTERNATIONAL JOURNAL OF SYSTEM ASSURANCE ENGINEERING AND MANAGEMENT 2019年第6期10卷 1535-1543页

作者： Ranjan, Rakesh Shastri, Vastoshpati Banaras Hindu Univ DST Ctr Interdisciplinary Math Sci Varanasi 221005 Uttar Pradesh India Govt Arts & Sci Coll Dept Stat Ratlam India

This paper deals with the well known bi-variate Weibull distribution developed by Marshall and Olkin. In the light of prior information, this paper derives the posterior distribution and performs Markov chain Monte Carlo methods to obtain posterior based inferences. This paper also checks the sensitivity of posterior estimates by changing the prior variances followed by Bayesian prediction using sample-based approaches. Numerical illustrations are provided for real as well as simulated data sets.

关键词： Bivariate model ML Estimates MCMC Gibbs sampler metropolis algorithm Predictive simulation

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Quantifying heterogeneity of stochastic gene expression

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JOURNAL OF THEORETICAL BIOLOGY 2019年 465卷 56-62页

作者： Iida, Keita Obata, Nobuaki Kimura, Yoshitaka Tohoku Univ Grad Sch Med Sendai Miyagi 9808575 Japan Tohoku Univ Grad Sch Informat Sci Sendai Miyagi 9808579 Japan

The heterogeneity of stochastic gene expression, which refers to the temporal fluctuation in a gene product and its cell-to-cell variation, has attracted considerable interest from biologists, physicists, and mathematicians. The dynamics of protein production and degradation have been modeled as random processes with transition probabilities. However, there is a gap between theory and phenomena, particularly in terms of analytical formulation and parameter estimation. In this study, we propose a theoretical framework in which we present a basic model of a gene regulatory system, derive a steady-state solution, and provide a Bayesian approach for estimating the model parameters from single-cell experimental data. The proposed framework is demonstrated to be applicable for various scales of single-cell experiments at both the mRNA and protein levels and is useful for comparing kinetic parameters across species, genomes, and cell strains. (C) 2019 Elsevier Ltd. All rights reserved.

关键词： Stochastic process Master equation Lac operon metropolis algorithm

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Classical critical dynamics in quadratically driven Kerr resonators

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Physical Review A 2020年第4期101卷 043826-043826页

作者： Wouter Verstraelen Michiel Wouters Theory of Quantum and Complex Systems University of Antwerp B-2610 Wilrijk Belgium

Driven-dissipative Kerr lattices with two-photon driving are experimentally relevant systems known to exhibit a symmetry-breaking phase transition, which belongs to the universality class of the thermal Ising model for the parameter regime studied here. In this work, we perform finite-size scaling of this system as it is quenched to the transition, and the dynamical critical exponent is found to be compatible with z≈2.18, corresponding with metropolis dynamics in classical simulations. Furthermore, we show that the Liouvillian gap scales with the same exponent, similar to scaling of the Hamiltonian gap at quantum phase transitions in closed systems.

关键词： Cavity quantum electrodynamics Dynamical phase transitions Open quantum systems & decoherence Quantum quench Quantum cavities Finite-size scaling metropolis algorithm Stochastic differential equations

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Order-disorder versus displacive transitions in Jahn-Teller active layered materials

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Physical Review Materials 2020年第4期4卷 043601-043601页

作者： Maxwell D. Radin John C. Thomas Anton Van der Ven Materials Department University of California Santa Barbara Santa Barbara California 93106-5050 USA

Large anharmonic vibrations often play a crucial role in dynamically stabilizing crystalline phases whose structures are unstable at low temperature. Although the average structure of such phases can be measured through diffraction experiments, their local structure remains a challenge to characterize and understand. Dynamically stabilized phases are often classified as order/disorder or displacive based on the qualitative nature of their local structure. A robust understanding of how chemistry determines this distinction in behavior, however, is lacking. This article presents a parametric study of an anharmonic vibrational model that describes the transition from a cooperative to a noncooperative Jahn-Teller distortion in layered oxides—a class of materials widely used in Li-ion and Na-ion batteries. The results illustrate how the shape of the energy landscape determines the extent to which the high-temperature phase has order/disorder vs displacive character. We find that the nature of the high-temperature phase is determined by a competition between the strength of the elastic coupling between Jahn-Teller distortions at nearby sites and the energy scale driving the Jahn-Teller distortion. A comparison of the model to energy landscapes calculated with density-functional theory suggests that the high-temperature phases of the Jahn-Teller active layered compounds LiNiO2, NaNiO2, LiMnO2, and NaMnO2 exhibit order/disorder character.

关键词： Anharmonic lattice dynamics Jahn-Teller effect Structural phase transition Batteries Transition metal oxides DFT+U Hybrid functionals metropolis algorithm

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